"Tim Wescott" <[email protected]> wrote in message
news:[email protected]..
> Raymond Toy wrote:
>
>>>>>>>"Tim" == Tim Wescott <[email protected]> writes:
>>
>>
>> Tim> I'm trying to think of examples where using an anti-alias filter
>> is a
>> Tim> bad idea, or must at least be approached with extreme caution.
>> I
>> Tim> already know about control systems and video applications, and I
>> Tim> believe that this is a big issue with EKG machines.
>>
>> Isn't there always some kind of anti-alias filter, whether you want it
>> or not? Or are you saying that aliasing is better than whatever
>> artifacts an anti-aliasing filter would produce?
>>
>> Just curious,
>>
>> Ray
>
> There's always some sort of filtering going on, because no system has
> infinite bandwidth. I _am_ saying, however, that in many instances (such
> as EKG strips, video, or control systems) aliasing is better than the
> artifacts that you'd get from a filter that you could honestly call
> "anti-aliasing".

Tim,

As you know, it's all about what you mean by "honestly".
No real filter is perfect for theoretical anti-aliasing purposes.
Many real signals don't threaten to cause aliases that are troublesome.
Of course, there is always a pathological case that one can theorize
about....

Fred